FIG. 1 depicts a schematic diagram of telecommunications system 100 in the prior art. Telecommunications system 100 comprises telecommunications terminals 101-1 and 101-2, network 110, and server 120, interconnected as shown. Network 110 is a communications network such as the Internet, the Public Switched Telephone Network (PSTN), etc., as is well-known in the art. Telecommunications terminals 101-1 and 101-2 are devices such as personal computers, telephones, etc. that communicate with other telecommunications terminals via network 110. Each telecommunications terminal has an associated contact identifier (e.g., telephone number, email address, Internet Protocol address, etc.) that uniquely identifies that terminal in the address space of telecommunications system 100. Server 120 (e.g., a Session Initiation Protocol [SIP] server, an SIP proxy server, etc.) maintains a list that maps user identifiers (e.g., user names, social security numbers, etc.) to contact identifiers.
Server 120 enables the users of telecommunications terminals to communicate as illustrated by the following example: A first user, the user of telecommunications terminal 101-1, enters a command into the terminal to place a call (e.g. voice call, email, text chat, video, etc.) to a second user. Telecommunications terminal 101-1 sends via an appropriate protocol (e.g., the Session Initiation Protocol [SIP], etc.) a message (e.g., an SIP INVITE message, etc.) server 120 that requests the contact identifier of the telecommunications terminal associated with the second user (i.e., the terminal that the second user is currently using). Server 120 then sends a response (e.g., an SIP acknowledgement [ACK], etc.) to telecommunications terminal 101-1 that indicates whether the second user can be reached, and if so, the associated contact identifier. Upon receiving the associated contact identifier, telecommunications terminal 101-1 sends one or more messages directly to telecommunications terminal 101-2 via network 110, and telecommunications terminal 101-2, which obtains the contact identifier of telecommunications terminal 101-1 via the received message(s), can respond directly to telecommunications terminal 101-2 via network 110.
FIG. 2 depicts a schematic diagram of wireless local-area network 200 in the prior art, which comprises access point 201 and wireless terminals 202-1 through 202-N, wherein N is a positive integer, interconnected as shown. Each wireless terminal 202-i, wherein i is member of the set of positive integers {1, . . . N}, is a device (e.g., a notebook computer, personal digital assistant [PDA], tablet PC, etc.) that communicates wirelessly with other terminals in network 200 via access point 201.
Access point 201 and wireless terminals 202-1 through 202-N transmit messages over a shared-communications channel such that if two or more wireless terminals (or an access point and a wireless terminal) transmit messages simultaneously, then one or more of the messages can become corrupted (which results in a collision and the destruction of both messages). As a consequence, local-area networks typically employ protocols for ensuring that a wireless terminal or access point can gain exclusive access to the shared-communications channel for an interval of time in order to transmit messages without collisions.
Such protocols can be classified into two types: contention-based protocols, and contention-free protocols. In a contention-based protocol, wireless terminals 202-1 through 202-N and access point 201 compete to gain exclusive access to the shared-communications channel.
In a contention-free protocol, in contrast, a coordinator (e.g., access point 201, etc.) grants access to the shared-communications channel to one station at a time. One technique in which a coordinator can grant access to the shared-communications channel is polling. In protocols that employ polling, stations submit a polling request to the coordinator, and the coordinator grants stations exclusive access to the shared-communications channel sequentially in accordance with a polling schedule.
The Institute of Electrical and Electronics Engineers (IEEE) 802.11e specification is an emerging set of protocols that provides quality-of-service (QoS) for wireless local-area networks, in addition to contention-based and contention-free shared-communications channel access. Quality-of-service is an important consideration for wireless local-area networks given the serialization of communications imposed by the shared-communications channel, as well as the growing bandwidth requirements of various applications. An IEEE 802.11e-compliant wireless terminal can transmit to the wireless access point a request to add a traffic stream (ADDTS), accompanied with the following information:                (i) a traffic specification (TSPEC) that specifies one or more parameters of future traffic that will be generated by the terminal (e.g., a temporal period for periodic traffic streams, a minimum service interval, a maximum service interval, etc.); and        (ii) a traffic class that indicates the priority of future traffic.        
The access point will either accept or decline the request, depending on the available bandwidth. If the request is declined the station may not transmit with the privileges of the traffic class indicated in the TSPEC. The ability of an access point to decline an ADDTS request enables bandwidth management, also known as “over-the-air admission control.” request enables bandwidth management, also known as “over-the-air admission control”.